Television transmission apparatus



Feb. 3, 1931. WA 1,790,736

TELEVIS ION TRANSMISS ION APPARATUS Filed Aug. 50, 1929 4 Sheets-Sheet 1 Feb 3, 1931. G. WALD TELEVISION TRANSMISSION APPARATUS Filed Aug. 30, 1929 4 Sheets-Sheet 2 Feb. 3, 1931. a. WALD TELEVISION TRANSMISSION APPARATUS 4 Sheets-Sheet 3 Filed Aug. 30, 1929 Feb. 3, 1931. G, WALD 1,790,736

TELEVISION TRANSMISSION APPARATUS Filed Aug. 30, 1929 4 Sheets-Sheet 4 45- of the television receiving Patented Feb. 3, 1931 Venom]: warn, einnmnvrnm, rumors 'nnvrsron rmsmssrox arrasaa'rus Application fled au m so, 1920. Serial it. seam.

This invention relates to improvements in.

television transmission apparatus.

An object of the invention is to produce a television transmission ap aratus, includv ing a light-sensitive frame t at will convert images into amplified electric current impulses that may transmitted to a receiver for reproduction, by direct reflection of the image on the frame. which 'is equipped with light-sensitive cells, whereb the electric current impulses are controlle b the variation in resistance resulting from te varying degrees of light reflected from the image.

The full scope and objects of the invention 5 will be apparent from the following detailed description taken in connection with the ac-- companying drawings, inwhich Fig. 1 is a composite illustrative view of the receivin frame illustrating optional forms of lig t-sensitive cells together with the electrical connections therefor.

Fig. 2 is an enlar (1 view of a pair of light-sensitive cells i ustrating the current path therethrough.

Fig. 3 is a side view partiall in section, illustrating the constructlon of t e grid rods in association with the'light-sensitive cells and the elements whereby the light-sensitive cellsare connected into the circuit.

ment.

Fig. 5 is a diagrammatic view of the grid element with the complete electrical circuits therefor.

Fig. 6 is an enlarged view, in vertical section, of a pair of light-sensitive cells showing the detailed association of the grid rods therewith.

Fig. 7 is a front view of the assembled receiving frame, portions being broken away to fully illustrate the complete construction of the unit and its connections.

Fig. 8 is a view, partially diagrammatic and partially in section, illustrating the side apparalus includocusingthe image ing the lens system f on the receiving frame.

Fi 9 is an illustrative diagram showin the a ternating current parallel circuits an I the current path in each.

Fig. 4 is a bottom plan view of the grid ele- .Fig. 10 is a diagram further illustrating the principles of the circuits involved in the apparatus.

The sendin apparatus includes a vacuum tube having a base piece 1 from which prongs 2, 3, 4, 4a, 5, 6 and 6a project, said pron being connected at their inner ends wit the internal leads of the respective circuits and their outer ends being adapted to contact with the external leads when the base 1 is mounted in a socket. The base piece 1 supports a tube 7 which is preferably shaped as shown in Fig. 7, being substantially rectangular in outline with the front and back walls spaced apart and the top and side walls rounded. The' tube is flask-shaped.

The grid element is made up of a of flat plates 8 preferably arran e allel series with the ends of eac plate oflset, as shown in Fig. 4. The plates I 8 are mounted on the back of a plate 9 of in paralternate "thus substantially Lplurality insulating material. A plurality of series of grid rods 10 extend at right angles to the plates 8, each of said rods having a reduced extremity 11 that passes through an opening in the plate 9, the rods of each series be- 7 ing respectively electrically connected to one light-sensitive cells'and a plurallty of series 0 conductors 14. i

In Fig. 1 of the drawing optional forms of I the light-sensitivo' eells are s own, the manner in which'they are constructed is as followsz'In the face of the'plate 12 there are formed series of molded cavities in parallel groups in which are seated strips of stam ed conductor member-e of the form and out ine shown in the optional views in Fig. 1. In the upper broken panel of Fig. 1 is shown a series of intersectin circles arranged in rallel groups the a jacent parallel groups mg conn so that each conductor com- ,inglymade to accommodatethe selected form.

- alpproximately 1/100 of an inch deep, an

.the discs have -rial is annealed to approximately 180 C.,

The cavities in the plate 12 are very shallow e conductor strips 14 of either selected form are inserted in the cavities so that within the area defined by the contour of the conductor lates there remains a slight depression. n mounting the conductors inthe plate 12 the cross dimension. of each circle, hexagon, or squareis slightly greater than the cavities as originally. formed in the late 12,50 that when the edges of the con uctor strips are pressed into the cavities, a slight sprin action will be exerted against the walls 0 the cavities to hold the conductors in place. After the conductors have been thus mounted the internal spaces defined by the conductors are filled with melted selenium, or other light re-acting material, and the surplus scraped or removed from the entire plate so as to leave the selenium orfother material .in a thin disc form, thereby formin the cell discs 15. After thus been molded, the matethereb forming a permanent conductive variab e resistance connector between the walls of each cell through which current flows under certain conditions hereinafter more fully explained.

Each of the grid rods 10 has an upper reduced portion 16 that extends through the plate 12 and terminates in' respective ones of the cell discs 15, the oint of each rod being embedded in such ce disc.

Inmmbling thegrid element. the grid rods are held in a template and the plate 9, with the suitably formed openings-therein, is lacedrover the ends of the rods with the r uced portions 11 extending through. the openin The plates 8 are t en assembled and the ends of the reduced portions 11 of the 'd rods are flattened or riveted over to old them in lace. The template is then removed and t e plate 12, provided with the to clam phthe plates 9 and 12- ove r the grid a suitably-formed openings,.is mounted overthe op osite ends of the grid rods with the reduce portions 16, extending through saidopenings, and the spacing rods-3:3 assembled rods. e conductors. 14 are then set in place in the cavities formed in the upper'face of the plate 12', and the selenium or other.

light reactive material is moulded into the 'The primary quency current of, for example,from 200 to able condensers.

cavities defined by the contour of the conductor plates 14, thus completmg the grid element.

At one side of the conductors 14, and with- .in the tube 7, is an induction coil 17. The

separate conductors 14, comprising two branches, are tapped into the induction C011 17 at equidistant points through tap leads 18. The lower end of the coil 17 is connected by a lead 19 to the prong 6 in the base piece 1.

The plates 8 are respectively tap ed in by tap leads 20 to an induction coil 21. ormed in two branches, the lower end of said coil being connected with the prong 4 by a lead 22.

The grid circuits maybe understood by reference to the diagram shown in Fig 5. A variable frequency current is received on a primary 23. The frequency of the current, for example, is from 100 to 105 rkllOCYClGS. The current is impressed on the secondary 24. A variablecondenser 25 functions to tune the secondary with the circuits for the conductor 14. This variable frequency, becauseof the balancing of the induction and capacity of the circu1ts,produces resonance in sequence in the separate conductors. 14. That is to say, a circuit is so tuned that resonance willbeproduced imthe upper one of the series of conductors 14' at 100 kilocycles frequency and in the lower one of the series of conductors 14 at 105 kilocycles frequency, the frequency attained intermediate these two limits producing resonance in the interme' diate conductors,

26 receives a variable fre 205' vkilocycles which is impressed upon a.

secondary 27. A variable condenser 28 functions to tune the" secondary 27 with the circuits for the plates 8-. The secondary produces resonancein the plurality of plates 8 so that one end of the series responds at 200 kilocycles and the other end of the series at 205 kilocycles, with the intermediate plates being brought under resonance by intermediate fre uencies; I

In my atent No. 1,7 54,491, granted April 15, 1930, I have shown a' general system for transmission and reception of" television in which there is em loyed synchronized varit ismy purpose to use that construction to energize the primaries 23 and 26, respectively, 'of' the present application. 7

Because full description of the construction ofthe condensershas been givenin my said patent, it isunnecessary to repeat the construction here, suilice it to say that the trans former 23 24 of the resent ap lication corresponds to the trans ormerl54 o 1 my said 5 patent, and-that the tr a'nsformer.26-27 of the present applicationcorresponds to the Y transformer 48 ofmy copendin application. -As aresult of, theoperation o thesynchronized variable condensers of the said patent there is impressed upon the primaries 23 and -26 of the present application synchronized bands of variable frequency.

Since all of the conductors 14 are tapped at equidistance across the coil 17, and all of the plates 8 are tapped at equidistance across resonance from top to bottom of the con- I ductors 14.-

In order better to understand the phenomenon-which is the basis of operation of the apparatus reference may be made to the diagrams in Figs. 9 and 10, and to a brief consideration of the mathematics involved. The

equation of a resonant condition must be such that 1 j 21 11] where f is the frequency of the current, L the inductance in henries, and C the capacity in farads. Now, by reference to Fig. 9, there will be found a main circuit 29 and a parallel circuit of branches 29a, 29b, 29c and 29d, each branch circuit having a progressively increasing inductance, and a branch 29a which includes a variable condenser. Let it be assumed that the alternating current is applied across this circuit, and that f has such a value that L of the branch 29d satisfies the resonance equation above given. Then, it follows that the values in amperes of the respective currents in the circuits will be as shown in thecalculations above the arrows in the diagram (Fig. 9), and that the current flow willbe in the direction indicated by the arrows. g

In this case the inductive reactance causes a current to lead the F. by a phase angle of 90, while the capacitative rea'ctance causes the current to lag 90. That is to say, due to capacity the current is 180 behind the current due to induction. Therefore, the current flow is in the opposite direction 180 electrically displaced. Again, by reference to the diagram it appears that the-main circuit has 10 amperes going to the right; that the branch 29a has'2 amperes g'the branch 29?) has 2 amperes and the branch 290 has 3 amperes going in the same direction, while the branch 29d has 103 ampereslikewise flowing in the same direction simultaneously with the current flow of 100 amperes in the opposite d1- motion, and that in the branch 29a there is a current of 100 amperes in both directions.

suming E equal to the'applied E. we

have

that is the total E acting in the branch circuit divided by the ohmicresistance of the branch circuit produces a maximum current, it being understood that E is a composite of E due to ohmic, induct-iveand capacitative developments. Thus, it is seen in a branch circuit where resonance exists, that the .ohmic' resistance determines the maximum quantity of current in the branch.

o IR, I representing the current and" The description has been made regard to Fig. 9 but it will be understood-that Fig. 10

substantially duplicates the diagram'in Fig. 9, with the exception that inrFig. 10 the inductance is added to each branch in series by tapping one induction coil at different points, thus. producing gradually increasing induction in the branches 29a to 29d. Therefore, since Fig. 10 represents; principle of'the grid circuit hereinbefore described, the phenomena of resonance with the mathematics involved may be understood from the foregoing description.

Returning now to the light-sensitive frame hereinbefore described, it should be understood that the apparatus is so designed that w an image 30 may be reflected through alens system 21 connected with a bellows 32, so that the image in magnified form may be cast upon the area containing the light sensitive cells. As the resistance of the selenium is subject to the light shades reflected from the image, and as the ohmic resistance of each cell is the main ohmic resistance of'its respective grid rod circuit, it follows that while each grid rod has some current in its circuit which varies with the resistance of its respective selenium cell, yet the total amount of all of the grid rod currents is less than the current in the grid rod circuit which is under 'resonance.v

The current is then divided among all of the grid rod circuits. The current in the grid circuit under resonance is independent of the line volta e, but is ,de endent on the total voltage (0 mic, inductive, and capacitative) in its branch circuit. The normal current that flows through the conductors '14, except in such cell'as may be under resonance which is brought about as above described, is through the path of least current'is no longer throughout the conduc resistance, namely around the metallic conductor member, and rcsultsin no impulses emanating from that portion of the frame. When aparticular cell is brought under res.-' onance the path of the greatly augmented tor strips, but is from the wall of the particular cell through the selenium disc, and

through the corresponding grid rod. Since the resistance of the selenium discis directly responsive to light and shade, the? current that passes through the. cell disc under resonancewi-ll' vary. within limits, as determined by the, varying resistance resulting from the light and shade. This current passing through the grid rod is amplified. By references to Fig. 2 it will be seen the current patli of a cell under resonanceis clearly illuss t trated diagrammatically.

The means for amplfying the current comj prises "the. usual three-electrode principle.

The apparatus includes a plate circuit. .The plate 35 is mounted in the tube and embraces three sides of-the grid rod bank. The plate 35, in the form of a U-shaped strip, is mounted between the plates 9 and 12 and is connectedby a lead36 with the prong 2, whichconnects with a lead 37 through the primary 38 otthe television output trans-' former. This, plate35 is-covered outwardly K with electrical insulating material so that the electronic flow from the filament will be through the grid rods 10. The circuit from the primary 38 is completed through a lead 39 to a source of power 40; the opposite end of the power element being connected with the common filament lead 4]. which, iriturn, conan alternating current will flow througheach needs with the prong 3 constituting one termi nalof the filament42; v The opposite'terminal of the filament 42 is the prong 5 which connectswith the variable resistance element 4.3 in circuit with a filament source of power 44;.

I have shown above where the filament 42, grid rods 10, and one side of the plate 35 are enclosed'within-the: chamber .formed (Fig. 8) by plates 9and 12 and the outerinsulative material on plate 35. It was also shown that grid rod 10'successivel y one after theother, correspondin to the resonanceacross the corresponding se e ctor. From the circuits shown i Fig. 5 it will be seen hat the currentfin the plate circuit, plate 3 36, 2, 27, primary 38, 39, B-power 40, 41, 3 and filament 42,

will likewise be an alternating current, ,like

' that induced'in the grid rod 10, but amplified in magnitude. I The amplitude of each,

" alternating current wave will'be that'which I "the corresponding gridrod has attach instance. The current in the secondary 45 will The impulses in the secondary television output circuit may .be received by an apparatus such, for example, as that shown'in my 3 Patent No. 1,7 54,491, or in my copending ap-- plication, Serial No. 373,076.

In Fig. 1 I have illustrated various optional forms of the conductors 14a dot the cells use of the selenium material for thedight'reembraced therein. The cons'deratioli that induces the preference for the form shown in the upper broken panel is that the current pathis etaual fromthe cell wall to the center of the cel disc at which pointthe grid rod'is positioned. It has a disadvantage in that I the space between the cell walls is dead space, unresponsive to light, and-therefore the sensitive area is not coextensive with the reflected image. Due to the increased size of the image, this will have little practical effect on the tele vision impulses generated by the apparatus. The middle broken panel in which the cells are in the form of hexagons has the very distinct advantage of minimizing the dead space, but results in a variable current path through the v resistance discs. The connected squares shown in the lower broken panel respond closely to a straight line transmission of the image andhas the advantage in that the dead space. is considerably minimized, In prac- I tlcaloperation the selection between the 011s forms of cells is optional.

vari- It should be noted in connection with the active discs, that the usual lag; causing selen um to be discarded in connection with television, 1s notjpresent inthe instant apparatus, because the several selenium 'cells 1 are under the influence of light and remain continuously reactive, and are not subject to instantaneous variations of. light. period. of excitation of the several cells is so The I short in durationthat the physical roperty of solenium is no disadvantage, stltutes rather an advantage in that if there be a movement of the image the response in the I solenium disc is not prompt enough to regthen be an alternating current "of variable wave length and' of an intensity correspondingto current produced by the light and dark shades of the image focused on the light-..

actuated cells 15.

ister the' blurred line that would result if the selenium wereinstantaneously responsive.

ut con- I The size of the image to be transmitted by the apparatus does not necessarily correspond to the area or the frame A 1" x 1" image maybe reflected ona 10" x 10" frame, for example by enlargement through a lens systerm. It is contemplated that by a sixty line l to the inch picture, the cells shall be approximately one-sixth of an inch in diameter;

that for a fifty line to'the'inch picture, ap-. proximately one'fifth of an inch. ,'Th1is,'the

plate may be ten times the size of the image;

When I the distance from the lens to the frame is'relatively large, provision should be made to maintain the, intervening space under vacuum so that there 'will not be,any refiec ,tioncor refraction of the light rays reflected 13% the image, This, however, isunnecescell, or cathode ray cell, which would be responsive to the light reflected from the image.

I am aware that the invention may be modified in numerous particulars without departure from the spirit and scope thereof.

1 do not limit myself unessentially, but

I what I claim and desire to secure by Letters Patent is 1. A television transmission apparatus 1 comprising a frame composed of a series of conductors adapted to receive electrical impulses of varying frequency, light-sensitive var ing resistance cells electrically connected wit said conductors, a second series of conductors adapted to be excitedby impulses of varying frequency, grid rods intermediate the respective cells and said second series of conductors, circuits for exciting said first named conductors, circuits for exciting said second named conductors, and means for bringing said circuits into resonance.

' 2. A television transmission apparatus comprising a' frame composed of a series of conductors adapted to receive electrical impulses of varying frequency, light-sensitive varying resistance cells electrically connected with said conductors, a second series of conductors adapted-to be excited by impulses of varying frequencies, grid rods intermediate the respective cells and said second series of conductors, circuits for exciting said first named conductors, circuits for excitin said second named conductors, means for ringing said circuits under resonance and thereby exciting the grid rods with electrical impulses of varying amplitude, and means for amplifying the impulses of the separate grid rods.

3. A television transmission apparatus comprising a frame composed of a series of conductors adapted to receive electrical impulses of varying frequency, li ht sensitive varying resistance cells electrical y connected with said conductors, a second series of conductors adapted td be-excited by impulses of varying frequency, grid, rods intermediate the respective cells and said second series of conductors, circuits for exciting said first named conductors, circuitsfor excitin said second named conductors, means for ringing said circuits under resonance and thereby exciting the grid rods with electrical impulses of varying amplitude, means for amplifying the impulses of the separate grid rods, 'an means for transmitting said amplified impulses for reception.

et. In an apparatus ofthe class described a light-sensitive frame comprising a series of metallic conductors, a pluralit of ii htsensitive discs embraced ,witbm conducsaid secon tors and in electricalconnection therewith, a circuit for exciting said conductors by varying fre'guency electrical impulses, a second series 0 con uctors, means or exciting said. second series of conductors by varying frequency im ulses so co-ordinated that all of series ofconductors will be excited while one of the first series of conductors is excited, grid rods connected with said light-sensitive cells at one end and with said second series of conductors at the other end and adapted to be energized when the .cir cuits for said second series of conductors operate to bring a selected cell under resonance, and means for amplifying the grid rod impulses.

5. In an apparatus of the class described a light-sensitive frame comprising a series of metallic conductors, a pluralit of ii htsensitive discs embraced within t e con uctors and in electrical connection therewith, a circuit for exciting said conductors by varyingfreguency electrical im ulses, a second series'o con uctors, means or exciting said second series of conductors by varying frequency impulses so co-ordinated that all of said second series of conductors will be excited while one of the first series of conductors is excited, grid rods connected with said light-sensitive cells at one end and with said second series of conductors at the other end and adapted to be energized when the circuits for saidsecond series of conductors operate to brin a selected cell under resonance, means or amplifying the grid ,rod impulses and means for transmitting said amplified impulses,

6. In an apparatus of the class described 7 a rectangular frame comprising a plate of insulating material, a pluralit of conductors set in said plate, said con uctors being 

